Air strainer



April 9 1938. c. c. FARMER 2,114,341

AIR STRAINER Filed June 3.6, 1936 2 Sheets-Sheet 2 INVENTOR ACBIYYDE c.FARMER.

Q/ I/d/ ATTORNEY Patented Apr. 19, 1938 UNITED STATES AIR STRAINER Clyde0. Farmer, Pittsburgh,. Pa., assignor to' The Westinghouse Air BrakeCompany, Wilmerding, Pa., a corporation of Pennsylvania Application June16, 1936, Serial No. 85,519

24 Claims.

This invention relates to fluid pressure systems and more particularlyto means for cleansing fluid supplied to the system, the presentapplication being in part a continuation of my co-pending application,Serial No. 758,779, filed December 22, 1934. p

The desirability and advantages of cleaning air which is being suppliedto a fluid pressure system are well known by those skilled in the fluidpressure art, but since there are so many different types of systemswhere air cleaners or filters are'used, the present invention will, forillustrative purposes only, be described in connection with a railwayfluid pressure brake system where it is especially desirable andadvantageous to cleanse the air supplied thereto of foreign matter suchas dir t and moisture.

In a railway fluid pressure brake system the several fluid pressurecontrolled valve devices,

chambers, and conduits connecting the chambers and devices are chargedwith fluid under pressure by way of a brake pipe which forms a part ofthe system. The control of such valve devices is accomplished by varyingthe brake pipe pressure as is well known by those skilled in the fluidpressure brake art.

Fluid being supplied through the brake pipe of a fluid pressure brakesystem may contain particles of foreign matter so minute that it isdifhcult to prevent them from passing into the control valve devices,and as a result these particles accumulate on the working surfaces ofthe movable parts of the valve devices and may also accumulate in feedgrooves or other communications of small flow area, either or both ofwhich conditions may eventually cause sluggish action of the valvedevices or in some cases result in complete failure of said devices.Further if the particles of foreign matter are of an abrasive naturethey will cause excessive wear of the working parts of the valve devicesand ultimately the failure thereof. 9

It has been ascertained under actual operating conditions that while theair cleaners or filters usually employed in fluid pressure brake systemsdo separate large particles of dirt'from air being supplied to thesystem, they are not in every case so efllcient in removing minuteparticles of dirt from the air stream, and it is these latter particleswhich; if not removed by the strainer, are liable to accumulate in thevalve devices and seriouslyinterfere with their operation as abovepointed out. H

The principal object of the invention is to provide an improved aircleaning and filtering means for embodiment in a fluid pressure systemand which is adapted to remove both large and minute particles offoreign matter from the air being supplied to the system therebyeliminating the possibility of the above mentioned faulty 5 operation ofcontrol devices included in the system. v

In my aforementioned copending application I have disclosed an airstrainer device which is v similar in some'respects to the device of them present application but which comprises inner and outer concentricallyarranged tubular retainingmembers which are formed of wire mesh andwhich have laterally extending lugs holding the straining material inplace longitudinally of 15 the device, each of said lugs being formed bythe end loop of two adjacent longitudinal strands of the wire mesh whichproject beyond the outer annular strand.

of the mesh as'intended but rather on the opposite side, this lattercondition being possible by distortion of theannular end strand whichcan easily occur due to the inherent pliability of the mesh. From thisit will be seen that the lugs in some cases might extend more thanone-half of 30 the distance between the inner and outer retainingmembers so that whenthe strainer is secured in place in a casing theends of the annular bosses on the casing and the securing nut instead ofengaging the straining material as in- 35 tended will engage these lugsand, as a result oil this metal to metal contact, there may be smallopenings between the bosses and the lugs which will permit unwanted flowof uncleansed air from one side of the strainer to theother. 40

It has also been found in some cases that the bonds or connectionsbetween some of the longitudinaland annularstrands of the wire meshretaining members of the strainer device are not strong enough towithstand the torsional stresses 45 transmitted thereto by the securingnut or plug when the nut is being screwed to its proper securingposition, and as a result the retainers will be twisted by the action ofthe securing nut. The degree of such twisting may be such as to 50shorten the strainer device and may also cause the lugs, which hold thestraining, material in place, to straighten out. Safar as the cleansingof the air stream is concerned, the efiiciency of the strainer device isnot impaired by such dis-. 55

tortion as long as the strainer device is clamped in the casing, butwhen the device is removed from the casing for the purpose of cleaningit of foreign matter which it has collected, the filtering material,being inherently resilient, will expand and thereby protrude beyond theends of the retaining members if the'holding lugs have beenunintentionally straightened out as just described.

If the retaining members of the device have been shortened due to thetwisting of the wire mesh as above described, the strainer will be unfitfor further service for the reason that the proper engagement betweenthe straining material and the bosses of the casing and securing nutcannot be obtained, due to the movement of the securing nut to itssecuring position being limited.

A strainer device of the type disclosed in the present application andin my copending application before referred to is adapted to be cleanedof foreign matter, which it has collected, by a method in which one ofthe steps consists in rotating the device axially at a very high speedand it has been found that the expansion of the straining material, dueto centrifugal force, causes the lugs at the ends of the device tostraighten out, with the result that the straining material willprotrude beyond the ends of the retaining members and in some cases maybe forced out from between the retaining members, all of which is ofcourse very objectionable.

To provide the maximum rigidity to the strainer device, the wires of themesh are made of steel, but since steel will not withstand repeatedbending without breaking, it will be apparent that if the 'lugs of theretaining members are straightened out after having once been bentlaterally they are liable to break off in attempting to bend them againto their holding position, thus when the lugs are unintentionallystraightened out by the twisting of the retainers or by the action ofthe straining material while the strainer device is being rotated in acleaning machine, the strainer device is liable to be rendered unfit forservice by the breakage of the lugs in attempting to again bend them totheir holding position.

Another object of the invention is to provide a strainer devicecomprising inner and outer concentrically arranged foraminous hollowretaining members which are so constructed as to be free of all of theabove mentioned objectionable features. According to this object eachretaining member is made from a single piece of material such, forinstance, as a section of seamless tubing of brass or any other suitablematerial or a flat metal plate rolled or bent to hollow form and havingthe meeting edges of the plate soldered or otherwise secured together.

In practice it was ascertained that the wire mesh best suited for makingthe retaining members of a strainer device to be employed in fluidpressure brake equipments, where the strainer is limited both in lengthand diameter and where a certain amount of cleaning material must bepacked between the retaining members to insure the proper cleaning ofair which passes therethrough, is one which is woven of wire strands ofsmall diameter and number about nine per inch. If the mesh were woven ofwire of greater diameter either the diameter of the strainer would beincreased or the space into which the straining material is packed wouldbe reduced in width either of which conditions is objec- 1 With theabove in view it will be apparent that another advantage to be derivedfrom making each retaining member of the strainer device of a unitaryconstruction instead of woven wire mesh is that the openings throughwhich the air is adapted to pass may be reduced in number and soincreased in size thatlthe total flow area of the openings will beconsiderably greater than that of the openings of the wire meshheretofore employed, thus retaining members made in accordance with theinvention will offer less resistance to the flow of air than will thewire mesh members.

The wire mesh from which the retaining members have heretofore been madehas sixty-four openings per square inch whereas my improved retainingmembers have only sixteen per square inch. From this it will beunderstood that in the improved retaining members the bridging portionsbetween the openings may be made wider than the diameter of the strandsof the wire mesh and yet not impede or resist the flow of air throughthe strainer as much as does the strands of the wire mesh, all of whichcontributes to the increased efficiency and strength of the strainderdevice as a whole.

Other objects and advantages will appear in the following more detaileddescription of the invention.

As shown in the accompanying drawings, Fig. l is a side elevational viewof a strainer device embodying the invention and illustrating retainingmembers which are each made from seamless tubing; Fig. 2 is an endelevational view of the same; Fig. 3 is a fragmentary vertical sectionalview of a portion of a brake controlling valve device with the strainerdevice mounted therein, said device being shown in longitudinal sectionand Fig. 4 is a sectional view similar to Fig. 3 but made on a reducedscale and showing several of the working parts of the brake controllingvalve device and showing the strainer device in elevation. Fig. 5 is afragmentary side elevational view of the strainer device illustratingone way of constructing each of the tubular retaining members from asingle flat plate; Fig. 6 is a fragmentary end elevational view of thesame; Figs. 7 and 8 illustrate another way of constructing the tubularretaining members from a single fiat plate, Fig. 7 being a fragmentarylongitudinal sectional View of the strainer device and Fig. 8being across-sectional view taken on the line 88 of Fig. 7. Figs. 9 and 10 arecross-sectional views similar to Fig. 8 but each illustrating stillanother way of constructing each of the retaining members from a singlefiat plate. Fig. 11 is an end elevational view of a strainer embodyingthe invention and illustrating another form of the retaining lugs at theends of the retaining members. Figs. 12, 13, 14 and 15 illustrate stillanother form of the retaining lugs and the method of forming them, Fig.12 being a fragmentary plan view of the plate preparatory to forming aretaining member; Fig. 13 is a view similar to Fig. 12 but il1ustratinghow a portion of the plate is folded on itself to form the retaininglugs; Fig. 14 is a v fragmentary longitudinal sectional view of a how itfunctions when secured in place in a casing.

As shown in the drawings, the air strainer or,

filter device is preferably of cylindrical form and comprises inner andouter foraminated tubular members I and 2, respectively, which arepreferably of equal length and are arranged concentrically with respectto each other, the member 2 being made of greater diameter than themember I and surrounding or encircling the member I for its full length,so as to provide space between the members for the reception of airstraining material.

The retaining members are each provided at each end with a relativelyshort longitudinally extending imperforate annular web 4 and extend ingbetween and integrally connected to the inner ends of the webs 4 is theforaminated portion 5 of the member.

Surrounding or encircling the retaining member I is a sleeve or covering6 of porous material, such for instance as relatively thin felt or anyother material which will not offer any substantial resistance to theflow of air therethrough and yet will separate minute particles offoreign matter, such as dust, from the air as it passes therethrough.

The space between the covering *6 and the inner surface of the outerretaining member 2 is packed with a suitable straining material I, suchas curled hair, which is confined at each end of .the strainer device bymeans of a relatively thick flexible annular washer 8 which ispreferably made of felt and which fits snugly in the space betweenthe-covering 6 and the inner surface of the retaining member 2. The endof the covering 6 extends through the central opening in the washer 8and is flared outwardly as indicated by the reference character 9 intooverlapping relation with the outer surface of the washer.

It will be understood that the covering 6 besides serving to removeminute particles of foreign matter from air passing therethrough alsoserves to isolate the curled hair straining material from the core ofthe strainer device so that the possibility of portions of the strainingmaterial passing into the valve devices is entirely eliminated.

At each end of the strainer device the washer 8 and flared portion 9 ofthe covering 6 are retained in position between the members I and 2 bymeans of short lugs I and II which are bent laterally of the spacebetween the members, the lugs Ill when so bent extending outwardly fromthe annular web of the member land the lugs I I extending inwardly fromthe annular web of the member 2. As shown in the drawings these lugs arepreferably integral with the outer ends of the webs 4 of the members 'Iand 2.

The length of the lugs I0 and II is less than one-half of the width ofthe space between the members I and 2 so that there is a clear annularspace between the ends of these lugs in which annular bosses are adaptedto engage the outer faces of the washers 8 without a metal to metalcontact being made between the bosses and the lugs, all of which willhereinafter more fully ap-. pear.

As shown in Figs. 1 to 4, inclusive, the tubular retaining members I and2 may each be made from a relatively short piece of seamless tubingwhich may be of brass or any other non-rusting material or as shown inFigs. to inclusiveand 12 to inclusive may be made from a'flat platewhich is bent to tubular form and which has its ends soldered, welded,interlocked or otherwise secured together.

As shown in Figs. 5 and 6 each of the end edges of the plate from whicheach of the retaining members is formed comprises an imperforate web I2to which the longitudinally extending bridge of the plate and that oneweb of the plate from which the retaining member 2 is formed issimilarly offset in the opposite direction, so that when the end webs ofthe plates are secured together and the members incorporated in astrainer device, the inner and outer faces of the device will each be ofplain-circular form, that is to say will be free of projections.

As shown in Figs. 7 and 8 the end webs I2 of the plates may be providedwith folds 25 which are interlocked together and which are pressed intoclose engagement with each other to securely fasten the webs togetheragainst accidental separation or movement relative to each other. The

.folds in the webs I2 are so arranged that when the inner and outerretaining members I and 2 are incorporated in a strainer device theywill extend into the space between the members so that inner and outerfaces of the strainer device will each be of plain circular form as isthe case in.thestrainer device shown in Figs. 5 and 6. With this form ofjoint, the interlocking folds are preferably terminated short of theouter ends of the retaining members as shown in Fig. '7, thuseliminating the possibility of the folds distorting the inner and outeredges of the washer, which might otherwise occur and provide spacesthrough which air might flow without being properly cleaned.

As shown in Fig. 9, the outer ends of the end webs I2 of the plate maybe arranged in abutting relationship with each other and securedtogether by means of a narrow plate- I3 soldered or welded to'each web.

As shown in Fig. 10 the end webs I2 may be se cured together inoverlapping relation without ofiseting one of them. With this form ofjoint the outer surface of the outer retaining member will not of coursebe in the formof a true circle but where the strainer does not havetoflt snugly in a casing this will not be objectionable.

As shown in Fig. 11 the lugs I0 and II may be made wider at their basesthan at their ends instead of being of even width for their full lengthas shown in Figs. 2 and 6- In some cases themetaining members I and ofthe strainer device may be made of thinner material than that requiredin a strainer device for use in fluid pressure brake equipment but whenthinner material is used it is necessary to make the lugs at the ends ofthe membersstiif enough to withstand, without bending, the outwardlydirected pressure of the straining material when the strainer device isbeing cleaned in the cleaning device hereinbefore mentioned, andin Figs.12, 13 and 14 one way of doing thisis illustrated.

As shown in Fig. 12 the webs 4 at opposite sides of the plate from whicha retaining member is to be formed, instead of having spaced lugs formedat their outer edges, are extended in width and provided with openings21. To form the lugs the plate is folded back upon itself as 1 shown inFig. 13, the fold being on a line which passes through the openings 21midway between their ends. From this it will be seen that the lugs willbe spaced apart as in the retaining members hereinbefore described andwill be of two thicknesses of metal and will therefore have the requiredstiffness to withstand the action of the straining material when thestrainer device is being cleaned in a cleaning device.

After the lugs have been formed as just described, the plate is rolledinto tubular form and the meeting ends thereof joined together in anyone of the ways hereinbefore described.

In Fig. 16 a modified form of strainer device is shown which differsfrom the device hereinbefore described in that the ends of the covering6 are flared outwardly far enough to cover the ends of the curled hair 1and in that the washers 8 are omitted.

The preferred method of assembling my improved strainer device is tofirst bend the lugs I0 and II at one end of the retaining members and 2,respectively, to their retaining position to then flare one end of thecovering 6 outwardly, then with the retaining members standing on thelugs l0 and II in their proper spaced position with relation to eachother insert one of the washers 8 between the members and intoengagement with the flared portion of the covering 6 and lugs I0 and II,to then pack the straining material between the covering 6, washer 8 andretaining member 2, to then insert the other washer 8 between themembers and 2, to then flare the other end of the covering 6 outwardlyover the last mentioned washer and to finally bend the lugs I0 and II atthe other end of the retaining members to their retaining position.

From this it will be understood that if desired the lugs l0 and II whichare first bent to the 7 ing and its functioning when mounted will now bedescribed.

In Fig. 3 of the drawings, the strainer device is shown, forillustrativepurposes only, embodied in a fluid pressure brake controlling valvedevice which comprises a casing l4 having a fluid conducting passage l5which may be ;considered as leading from the usual brake pipe- (notshown) and also having a fluid conducting passage l6 which leads to theemergency piston chamber H of the valve device (see Fig. 4). Thepassages I5 and "5 are both connected to a chamber I8 containing myimproved strainer device which, during the assembly of the valve device,is inserted through an open threaded end of the chamber l8 and which issecured in said' chamber by means of a screw plug 19 which hasscrewthreaded connection with the casing within the open end of thechamber, said plug having a passage 20 leading from the chamber It! tothe'triple valve piston chamber 2| of the valve device.

The inner end of the plug I9 is provided with an annular rib 22 which ispreferably of V-shape in cross section and which engages the washer 8atone end of the strainer device within the clear space-between the endsof the adjacent lugs I0 and H and flexes the washer inwardly, as shownin Fig. 3,-as the plug is turned to. its normal securing .position. Atthe same time a similar rib 23 carried by the rear wall of the chamberl8 engages the other washer 8 in the clear space between the ends of theadjacent lugs i0 and II and flexes this washer inwardly. The washers 8being made of such material as felt, the ribs 22 and 23 become partiallyembedded in the washers a suflicient distance that there is no liabilityof there being any free open space between the strainer device and thecasing to permit leakage of uncleansed air from passage l5 to passagesl6 and 20 and thereby to piston chambers I1 and 2|.

The packed curled hair, due to its inherent resiliency and also duetothe flexing of the washers as just described, will closely engage thewashers 8 and the ends of the strainer so that there is no possibilityof the leakage of uncleansed air through the strainer at points adjacentthe washers.

In charging a fluid pressure brake equipment initially or to release thebrakes, fluid under pressure supplied to the brake pipe flo'ws throughpassage i5 to the chamber l8 and from thence strainer device, the curledhair I catches the large particles of foreign matter and the feltcovering 6 catches the particles which are too minute to be caught bythe curled hair. From this it will be apparent that a thorough cleaningof the air passing from the supply passage to the working parts ofthevalve device is insured.

As shown in Fig. 3 there is considerable clearance between the left handend of the strainer device and the casing and also between the righthand end of the device and plug l9 which serves to prevent the strainerdevice from being clamped in metal to metal contact with the casing andplug when due to slight inaccuracies in the manufacture of the casingand the plug the distance between the inner end of the chamber l1 andthe plug is less than that intended, thus insuring against thepossibility of the distortion of the retaining members by the action ofthe plug. It will here be understood that the ribs 22 and 23 by reasonof their engagement with the washers 8 and the outward pressure of thecurled hair 1 on the washers, the strainer device is rigidly held inplace in the casing against unwanted movement in any direction.

When the brake pipe pressure is reduced to effect an application of thebrakes, the consequent flow of fluid under pressure from the pistonchambers I! and 2| and through the strainer device will tend to detachand carry away from the strainer any foreign matter which may haveaccumulated therein, thus the strainer is rendered self-cleaning to suchan extent that the strainer may be used over a long period of timewithout-danger of becoming clogged. This selfcleaning action is mosteifective'when an emergency application is initiated for the reason thatthe brake pipe pressure and consequently the pressures of the pistonchambers l1 and 2| of the brakecontrolling valve device is reduced at arapid rate and to substantially atmospheric pressure. The flow of fluidfrom the chambers l1 and 2| in effecting an emergency application of thebrakes is through the passages I5 and 20. strainer device, chamber I8and a passage 24 which leads to the usual vent valve device (not shown)which establishes communication from thepassage 24 to the atmosphere.This passage 24 is relatively short so that the foreign matter blownfrom the strainer will be carried to' the atmosphere with the fluidbeing released from the piston chambers as well as from the brake pipe.l

While several illustrative embodiments of the invention have beendescribed in detail, it is not my intention to limit its scope to theseembodiments or otherwise than by the terms of the appended claims.

Having now described my invention, what I claim as'new and desire tosecure by Letters Patent, is: l 4

1. In a strainer, in combination, a hollow foraminous core havingoutwardly directed lugs at its ends, a foraminous body portionsurrounding said core and spaced therefrom and having inwardly directedlugs at its ends, there being clear space between the ends of the lugsof said core and the ends of the lugs of said body portion, a mass ofstraining material packed in the space between said core and bodyportion, and a ring of flexible material at each end of the strainerinterposed between said core and body portion and retained in positionby said lugs. 2. In a strainer, in combination, a hollow foraminous corehaving outwardly directed lugs at, its ends, a sleeve of perviousmaterial surrounding said core, a foraminous body portion surroundingsaid sleeve and spaced therefrom and having inwardly directed lugs atvits ends, the ends of the lugs of said core and the ends of the lugs onsaid body portion being spaced' and having inwardly directed lugs at itsends,

and a mass of straining material packed in the space between said sleeveand said body portion, said lugs acting to retain the respective flangesin position.

4. The combination with a fluid pressure operated device, of a strainerfor removing foreign matter from fluid supplied to said device, saiddevice comprising a casing having a bore through which fluid underpressure is adapted to be supplied to said device, said strainercomprising hollow foraminous core, a foraminous body portion surroundingsaid core and spaced therefrom, a mass oi straining material packed inthe space between said core and body portion, a ring of flexiblematerial at each end of the strainer interposed between said bore andbody portion, a retaining element adapted to be received in saidfbore toposition and retain said strainer, means in said bore adapted to engageone of said rings upon application of said retaining element, and meansassociated with said retaining element adapted to engage the other ofsaid rings, eachiof said means cooperating with the respective ring toeffect an air-tight seal against leakage of fluid-under pressure pastthe ends of said strainer and therebyinsure the passage of fluid throughsaid strainer.

5. The combination with a fluid pressure operated device, of a strainerfor'removing foreign matter from fluid supplied to said device, saiddevice comprising a casing having a bore through which fluid underpressure is adapted to be supplied to said device, said strainercomprising a hollow foraminous core, a sleeve of pervious mastrainer,means in said bore adapted to engage one of said rings and flex sameinwardly upon application of said retaining element, and meansassociated with said retaining element adapted to engage and flexinwardly the other of said rings, each of said means cooperating withthe respective ring to effect an air-tight seal against leakage of fluidpast the end of the strainer, the flexing of said rings acting tocompress the straining material therebetween to further in-' sure thepassage of fluid through said strainer.

6. The combination with a fluid pressure operated device, of a strainerfor removing foreign matter from fluid supplied to said device, saiddevice comprising a casing having a bore through which fluid underpressure is adapted to be supplied to said'device, said strainercomprising a hollow foraminous core, having "outwardly directed lugs atits ends, a sleeve of pervious material surrounding said core, aforaminous body portion surrounding said sleeve and spaced therefrom andhaving inwardlydirected lugs at its ends, the lugs on said body'portionbeing spaced from the lugs on said core, a mass of straining materialpackedin the space betweensaid sleeve and body portion, a ring offlexible material at each end of the strainer interposed between saidsleeve and body portion, a retaining element adapted to be received insaid bore to position and retain said strainer, means in said boreadapted to engage one of said rings in the space between the lugs onsaid core and on said body portion upon application of said'retainingelement, and means associated with said retaining element adapted toengage the other of said rings in the space between the lugs on saidcore and body portion, each of said means cooperating.

with the respective ring to effect an air-tight seal .against leakage offluid under pressure past the foraminous body,portion surrounding saidsleeve and spaced-therefrom and having inwardly 11-;

rected lugs at its ends, .the ,lugs' on said body' portion being spacedfrom th'e. lugs on said core,

1 a mass of straining material packedin the-space between said sleeveand body portion, a retaining element adapted to be received in saidbore to position and-retain said strainer, means in said bore adaptedtoengageand flexinwardly one of said flanges upon application of saidretubular members arranged one within the other,

each of said members comprising imperforate longitudinally extending endwebs and a foraminous portion extending between said end webs andconnected thereto, straining material interposed between said members,and lugs integral with said end webs for maintaining said strain-.

ing material in position with respect to said members, said lugsextending laterally from said webs and being deflected longitudinally ofthe members in directions toward said foraminous portions at an acuteangle to the web.-

9. In a strainer device, in combination, spaced tubular members arrangedone within the other,

each of said members comprising. imperforate longitudinally extendingend webs and a foraminous portion extending between said end webs andconnected thereto, straining material interposed between said members,and lugs integral with said end webs and extending laterally into thespace between said members for maintaining said straining materialwithin the outer end edges of said end webs, each of said lugs being ofless length than o'ne-half of the width of the space between saidmembers.

10. In a strainer device, in combination, spaced tubular membersarranged one within the other, each of said members comprisingimperforate longitudinally extending end webs an a :Eoraminous portionextending between said end webs and connected thereto, strainingmaterial interposed between said members, and spaced lugs extendingoutwardly from the outer end of each of said end webs and bent laterallyto a position for maintaining said straining material confined withinthe outer end edges of said end webs, the

ends of the lugs at each end of one member being spaced away from theends of the lugs at the same end of the other member.

11. In a strainer device, in combination, spaced tubular membersarranged one within the other, each of said members comprisingimperforate longitudinally extending end webs and a foraminous portionextending between-said end webs and connected thereto; strainingmaterial interposed between said members, and spaced lugs extendinglaterally from the outer end of each ing material retaining meansintegral with said webs and extendinglaterally thereof and beingdeflected longitudinally of the member in direcangle thereto.

13. In a strainer device, in combination, spaced tubular casing elementsarranged one within the tion's toward the ioraminous portions atan'acute other and each comprising a single piece of material havingannular end webs, a foraminated portion integrally connected to saidwebs, straining material between. said elements, and means carried bysaid webs and extending laterally thereof and inwardly in the directionof the toraminated portions ofthe members adapted to retain thestraining material between, said elements.

14. In a strainer device, in combination, spaced tubular membersarranged one within the other and each comprising annular end webs and atubular foraminated portion extending between and integrally connectingsaid end webs, straining material in the space between said members, anannular washer at each end of the strainer device interposed betweensaid members in the plane of said webs at the corresponding end of thestrainer and engaging said straining material, and means for retainingthe washers and thereby the straining material between said mem-. bers,said washers being resilient and pervious to air.

15. In a strainer device, in combination, spaced tubular membersarranged one within the other and each comprising annular end webs and atubular foraminated portion extending between end of the strainer forretaining the straining material between said members and means forretaining the annular washers between said members, said annular washersbeing resilient and a tubular member made of a flat plate bent totubular form and having its ends interlocked to form a rigid jointtherebetween, said member comprising spaced annular end webs and aforaminated portion extending between and integrally connecting said endwebs, said joint terminating short of the outer ends of said webs toprovide a plain inner surface for engagement by an annular strainingmaterial retaining washer.

18. In an air strainer, a retaining wall member comprising atubular-section having imperforate end webs and a foraminous connectingportion and straining material retaining lugs pro- Jecting laterallyfrom said webs, said lugs being deflected longitudinally of the memberin directions toward said foraminous connecting portion.

19. In a strainer device, in combination, spaced tubular membersarranged one within the other and each comprising annular end webs and atubular foraminated portion extending between and integrally connectingsaid end webs, straining material in the space between said members, anannular washer at each end of the strainer device interposed betweensaid members in the plane of said webs at the corresponding end of thestrainer and engaging said straining mate-' rial, a sleeve of perviousmaterial interposed between one of said tubular members and saidstraining material and covering the foramens in themember and beingflared over each washer, and means carried by said members for retainingthe washers and thereby the straining material between said members, theretaining means carried by the member having the ioramens covered by thesleeve clamping the flared portions of the sleeve to said washers.

20. In a strainer device, in combination, spaced tubular membersarranged one within the other and each comprising annular end webs and atubular ioraminated portion extending between and integrally connectingsaid end webs, straining material in the space between said members, anannular washer at each end of the strainer device interposed betweensaid members in the plane of said webs at the corresponding end of thestrainer and engaging said straining material, a sleeve of perviousmaterial surrounding the inner one of said tubular members and coveringthe foramens thereof and being flared at its ends over the inner edgesof said washers, and means carried by said members for retaining thewashers and thereby the straining material between said members, theretaining means carried by the inner member retaining the flaredportions of the sleeve in' overlapping relationship with said washers.

21. In a strainer, in combination, a hollow foraminous core havingoutwardly directed lugs at its ends, a foraminous body portionsurrounding said core and spaced therefrom and having inwardly directedlugs at its ends, there being clear space between the ends of the lugsof said core and the ends of the lugs of said body portion, strainingmaterial in the space between said core and body portion and two ringsof flexible matetion and arranged one at each end of the strainer andcovering the ends of the straining material,

rial interposed between said core and body por- 40 said rings beingretained in position by said lugs.

22. In a strainer, in combination, a hollow foraminous core havingoutwardly directed lugs at its ends, a ioraminous body portionsurrounding said core and spaced therefrom and having inwardly directedlugs at its ends, there beingclear space between the ends of the lugs ofsaid core and the ends of the lugs of said body portion, strainingmaterial in the space between said core and body portion and two ringsof flexible material interposed between said core and body portion andarranged one at each end of the strainer and covering the ends of thestraining'material, said rings being retained in position by said lugsand retaining the straining material positioned against movement indirections longitudinally of said core and body portion.

23. In an air strainer, a casing element comprising'a seamless tubehaving spaced annular end webs, a foraminated portion integrallyconnecting said webs, and spaced straining material re-'- taining lugsat each end of the tube extending in a direction across the end of thetube and deflected longitudinally of the tube in directions toward theioraminated portion.

24. In a strainer device, in combination, spaced seamless tubularmembers arranged one within the other, each of said members comprisingimperforate longitudinally extending end webs and a foraminous portionextending between said end webs and connected thereto, strainingmaterial interposed between said members, and lugs integral with saidend webs for maintaining said straining material in position withrespect to said members, said lugs extending laterally from said websand being deflected longitudinally of the members in directions towardsaid ioraminous portions at an acute angle to the web.-

CLYDE C. FARMER.

